1. Field
This invention relates generally to methods for location determination.
2. Background
In range-based location determination systems, time delay measurements of navigation beacon signals from a plurality of sources are converted to range information associated with the source of each navigation beacon signal. Ranges to different sources with known locations are combined to solve for the unknown user location via geometric techniques known, for example, as trilateration or multilateration. If the delay of navigation beacon signals cannot be known absolutely (e.g. in systems where the user clock is not synchronized to the network), location determination algorithms may treat user clock temporal bias as another unknown, to be solved for by the trilateration process, using an additional time delay measurement.
To improve position determination accuracy, receiving multiple navigation beacon signals (i.e., signal sources) is desirable. However, in many cases, weaker beacon signals (i.e., those farther away from the user receiver) are not detectable (and therefore not usable) since they are masked by stronger navigation beacon signals.
In an attempt to capture the weaker navigation beacon signals, previous techniques use a single antenna per user receiver. Detection of the weaker navigation beacon signals is attempted by using increased signal integration times to increase the sensitivity of the weaker navigation beacon signals.
Accordingly, it is desirable to provide a method for detecting navigation beacon signals with the use of two antennas or its equivalent thereof.